Electrical apparatus



Jan. 9, 1923. 1,441,532

P. R FORTIN. ELECTRICAL APPARATUS.

FILED JULY I, 1920 2 SHEETS-SHEET I 001 @999 men :0 I InVenEqr:

2/ 7 Paul R Forcm,

His Attorney Patented Jan. 9, 1923.

.iu Nl'rE sures- E OFFICE.

wit ;a.- roa'rm. or spnnnno'rnnxusw Your. assronon T GENERAL ELECTRIC COMPANY. A CORPORATION OF NEW YORK.

. ELECTRICAL APPARATUS.

Application and July 1, 1920. Serial No. 393,233.

To all whom it may com-cm lie it known that l. lM'i. ll. Harris, a citizen of thc l mted States, residlng at Schenectady, in the county of Schenectady,'

State of New York have invented certain new and useful Improvements in Electrical Apparatus, of which the following is a specification.

This invention relates to devices for vary ing the inductance of'an electric circuit, such for example, as those now employed in the wireless art. As is well known, in tuning a. high frequency circuit for the sending and receiving of waves of a definite. length, use

has commonly been made of an adjustable inductance called a variometer. lhis as usual consists of a plurality of coils movable relativel 7 to one another, So as to vary their mutual inductance. My present invention seeks to provide a device of this char-,

acter, which while compact and simple in construction shall permit of a" variation of inductance over a wide range. To this end an embodiment of the invention comprises a series of concentric cylinders, upon each of which is place(l a; plurality of coils, ad-

jacent coils on any one cylinder being oppositely wound. Alternate concentric cylinders are rigidly connected together and one of the sets thus formed is movable axially to vary the inductive relation between the coils of the two sets.

Referring; to the accompanying drawing,

Fig. 1 is a Side elevation of a device embodying my invention, certain of the parts of which are shown in section; Fig. 2 is a front elevation with the. panel hoard removed; Fig. 3 is an enlarged detail view showing the means for moving and indicating the portions of the cylinders; Fig. 4 is an enlarged perspective view of the removable operating knob; Figs. 5 and 6 are diagrammatic views showing the spacial arrangements of the coils and Fig. 7 'is a diagram showing the relation bctwcen the wave length and distance between adjacent coils.

Referring more particularly to l igs. 1. and 2, 10, ll, 12 and 13 represent a series of concentric cylinders, two of which II and 13 are stationary and secured at their forward end to the panel board 14. Cylinder 11 is also secured at its rear end by an upright 15. The remaining two cylinders 10 and 12 are supported l'rom a spider t6. the

'tions 26 on the knob arms of which extend through slots 18 and l!) in the cylinders 11 and 13. (in the pe-' riphery of each of these cylinders is wound a plurality of coils in and 21. On each cvliuder, coils 2U alternate with coils 2i aiul are oppositely wound thereto and all of the coils 2H and 21, are connected in circuit in series as is indicated. in Figs. 5 and (3. Cylinders 10 and 12 are adapted to he movcd in an axial direction by engagcmcnt of a screw 22 with a collar 23 secured to the spider It The screw 22 is operated from a disc 24 on the outside of the panel board through the connecting rod 25. Disc 24. in turn, .is rotated by engagement of projec- 27 with the sides of openings 28 formed in the face ofthc'disc. A pointer 29 is designed to indicate the position of the movable coils and in order to provide for aunution of the pointer 29 'that is considerably slower than that of the feeding screw 22,.thc pointer is secured to a tube 30 which rotates within a stationary casingiil. Tube. It" is providcd with in straightslot 32 and casing 31 with a hellca] slot 33'. Rod 2:7 is scrcn thrcadcd and carries an internally scrcwthrcaded collar 33 provided with a pin 34 which projects through the slot 32 into slot 33'. As the shaft'Ql is rotated to move the cylinders. pin 34 bcim mnst raincd to follow the ln'li cal slot 3.! incl. stationary casing 2H rotates, but a. fraction of the angle threaded by the screw 22, and in turning carries with it the tube I-ltland the pointer 29. i

To the rear of the iluluctamecoils are mounted the antenna plate and grid coils 35, 3G and 37. These arc employed in wireless transmission. but as they formno part of the present invention they will not be particularly descrilmd.

As shown in Fig. l, which represents one of the extreme positions of :uljustmcnt, coils 20, on each of the cylinders Ill and 12 Indirectly over the. oppositely wound coils 2| on each of the cylinders ll and II! and one of the coils 2| on each of the cylinders l and I2 lies directly over one of the oppositely wound coils 20 on each of the cylinders ll and 13. The twclvc coils of this group substantially neutralize one another and the remaining coils 20 on cylinders ll and l t, and coils 21 on cylinders 10 and [2 are the. only ones that are effective. The inductance ol' the circuit in this position is a minimum. In the other extreme position, which is indicated diagrammatically in Fig. 5, like coils lie directly within one another with the lesull: that their effects are additive and the inductance of the circuit is a maximum. The inductanccs may be adjusted to any value between the maximum and minimum by setting the coils in some intermediate position. setting approximately halfway between those shown in Figs. 1 and 5 is shown in Fig. 6.

In the practical construction of the variometer above described, particularly when the same is to he used on a ship or motor vehicle, economy of space is one of the factors to ho cimsidcred. in the spacing of the coils on the cylinders care should be taken on the one hand not to place them so close together that the inductive effect of one coil is largely destroyed by its prox imity to oppositely wound adjacent coils. nor on the other hand to place them so far apart as to require the use of extremely long supporting cylinders. The spacing of the coils at a considerable distance from one another gives rise to the disadvantage that in the manipulation of the variometer a range is encountered where a considerable movement of the operating means gives but a slight variation of imluctance. Fig. 7 shows the relation of the wave length to which a wireless sending or receiving apparatus is adjusted (plotted as ordinates) and the distance apart of the coils (plotted as ahscissic). it is preferred to space the coils so that the instrument will operate. in the ncighhorhoml of vertical line .-\-l$.

What I claim as new and desire to so cure hy Letters latcnt of the United States. is:

I. In an electrical apparatus. two series umncctcd o 'ipositely \vound coils and a third coil in series with said lirst, mentioned coils, said coils l cin; relatively movable between two positions in one of which positions said third coil and one of said first mentioned coils are arranged so that one lies within the other, and in the other of said positions said third coil and the other of said first mentioned coils lie in close inductive relation to one another.

.2. In an electrical apparatus, two series connected oppositely \vound coils, a third coil in series with said first mentioned coils, said coils being relatively movable between two positions, in one of which positions said third coil is in close inductive assisting relation to one of said first mentioned coils and in the other of said positions said third coil is in close inductive 0ppots-in; position to the other of said first mentioned coils. in one of said positions one of said coils lyin within the other.

3. In an electrical apparatus, two series connected oppositely \vound coils and a third coil in series with said filst mentioned coils, and movable from a position in inductive assisitinc relation to and within one of said first mentioned coils to a position in inductive opposing relation to and within the other of said first mentioned coils.

4. In a device of the character described, a series of coils arranged on concentric cylinders. alternate concentric coils being mechanically connected, and thereby forming two interspaced sets, and means for moving one set of coils axially with reference to the other set.

5. In a device of the character described,

a series of concentric cylinders, alternate cylinders being mechanically connected to form two interspaced sets. a plurality of coils, on each of said cylinders, adjacent coils on any cylinder being oppositely wound and means for moving one set of cylinders axially with reference to the other set from a position in which coils of one set lie directly \vithin assisting coils of the other set. to a position in which coils of one set lic directly \vithin opposing coils of the other set.

In witness whereof, I have hereunto set my hand this th day of June. 1920.

PAUL It. FQRTIN. 

